What is the smallest species of seahorse?

The smallest known seahorse species is Hippocampus satomiae, commonly called Satomi's pygmy seahorse.

Adults average only about 13.8 millimeters in length and approximately 11.5 millimeters in height, making them smaller than many human fingernails. The species lives among coral habitats in the waters around Indonesia, Malaysia, and Brunei, where its tiny body and camouflage help it blend into the reef.

Hippocampus satomiae was formally described as a new species in 2008. It was named after Satomi Onishi, a dive guide who collected the type specimens near Derawan Island in Indonesian Borneo. Its discovery highlighted how much marine biodiversity can remain hidden in seemingly familiar coral ecosystems.

The species is often confused with Denise's pygmy seahorse, Hippocampus denise, or the dwarf seahorse, Hippocampus zosterae. Those are also very small, but Satomi's pygmy seahorse is generally recognized as the smallest known seahorse. Pygmy seahorses are not merely baby versions of larger species; they are distinct species with specialized camouflage and miniature proportions.